Re: [PATCH v2 11/25] powerpc/8xx: map 16M RAM at startup

On Tue, 2015-10-06 at 16:10 +0200, Christophe Leroy wrote:

Le 29/09/2015 01:58, Scott Wood a écrit :

quoted

On Tue, Sep 22, 2015 at 06:50:50PM +0200, Christophe Leroy wrote:

quoted

On recent kernels, with some debug options like for instance
CONFIG_LOCKDEP, the BSS requires more than 8M memory, allthough
the kernel code fits in the first 8M.
Today, it is necessary to activate CONFIG_PIN_TLB to get more than 8M
at startup, allthough pinning TLB is not necessary for that.

This patch adds a second 8M page to the initial mapping in order to
have 16M mapped regardless of CONFIG_PIN_TLB, like several other
32 bits PPC (40x, 601, ...)

Signed-off-by: Christophe Leroy <redacted>
---

Is the assumption that nobody is still running 8xx systems with only 8
MiB RAM on current kernels?

No, setup_initial_memory_limit() limits the memory to the minimum 
between 16M and the real memory size, so if a platform has only 8M, it 
will still be limited to 8M even with 16M mapped.

And you just hope you don't get a speculative fetch from the second 8M?

-Scott